Approaches for improved frequency reuse efficiency and interference avoidance for a multi-beam satellite communications network

ABSTRACT

An RF communications transmitter system comprising a processor, a switch and a plurality of feedhorns. The switch is configured to receive a feed signal of a frequency bandwidth. The processor is configured to control the switch to provide the feed signal to each of at least two of the feedhorns for a respective time period. Each of the at least two feedhorns is configured to generate a beam during the respective time period that the feed signal is provided thereto, wherein the beam is formed based on the feed signal and is transmitted to cover a geographic area of the Earth. The formation and transmission of the beams by the feedhorns is controlled by the processor to provide a time-based allocation of bandwidth amongst the beams based on the time period that the feed signal is provided to each of the feedhorns and a respective frequency/polarization reuse scheme.

RELATED APPLICATIONS

This application is a continuation, and claims the benefit of priorityunder 35 U.S.C. § 120, from U.S. application Ser. No. 15/906,632 (filed2018 Feb. 27), which claims the benefit of the earlier filing date under35 U.S.C. § 119(e) from U.S. provisional patent application Ser. No.62/441,300 (filed 2016 Dec. 31), the entireties of which areincorporated herein by reference.

BACKGROUND

Multi-beam communications satellites (e.g., spot beam satellites) aredesigned such that a given geographic coverage area is serviced by apattern of beams. With such multi-beam satellites, in order to avoid orminimize inter-beam interference, certain frequency reuse principlesmust be applied to the bream patterns of the antenna design. One of theprimary guidelines for the beam pattern is that a frequency andpolarization combination of one beam cannot be “reused” within a certaindistance from another beam of the same frequency and polarizationcombination. The reuse distance between beams is generally specified asthe distance between beam centers of two beams of a same color (twobeams of the same frequency—the same frequency band and polarization),where the distance is quantified in terms of the center-to-vertex radiusr of the circumscribing hexagon representing the beams. If the minimumdistance requirements are not followed with regard to two such beams,then the beams will cause unacceptable levels of interference betweenthem. The beam pattern design is commonly referred to as a frequencyreuse pattern, where each polarization/frequency pair isdiagrammatically reflected by a beam color (or pattern in the case ofthe black and white figures included herein). In typical systems, areuse of four means that a set of four adjacent beams will have disjointfrequency and polarization assignments such that none of the beams ofeach set interfere with each other. In other words, adjacent sets offour beams separate the beams sharing a common frequency andpolarization such that (even though they are reusing the same frequencyand polarization assignments) the beams of one set will not interfereunacceptably with the respective beams of an adjacent set.

For example, FIG. 1A illustrates an example four-beam reuse pattern of asingle satellite 110, where, for example, the striped pattern 101reflects a right-hand polarization of a first frequency or frequencyband, the dot pattern 103 reflects a left-hand polarization of the samefrequency band as that of 101, the checkered pattern 105 reflects aright-hand polarization of a second frequency or frequency band, and thebrick pattern 107 reflects a left-hand polarization of the samefrequency band as that of 105. In such a four-color reuse pattern, thedistance between the beams or beam centers of two beams of the samecolor are 2√{square root over (3)}*r apart. As a further example, FIG.1B illustrates an example three-beam reuse pattern, where (similar tothe four-beam reuse pattern of FIG. 1A) each of the patterns 111, 113,115 reflects a particular beam frequency/polarization assignment. Insuch a three-color reuse pattern, the distance between the beams or beamcenters of two beams of the same color are 3*r apart. Accordingly, asillustrated by these Figures, each group of four or three particularpolarization/frequency beams is geographically arranged such that a beamof a particular polarization/frequency is not adjacent to any beam ofthe same polarization/frequency (where such beam pairs of a samepolarization/frequency are separated by a required minimum distance).

FIG. 1C illustrates example frequency band and polarization assignmentsfor the beams of the four-beam reuse pattern of FIG. 1A. Each Beam A,for example, comprises signal A in the frequency band 18.3-18.8 GHz (500MHz of spectrum for each such beam), applied to an RHCP feed of thedownlink antenna. Each Beam B comprises signal B in the frequency band19.7-20.2 GHz (500 MHz of spectrum for each such beam) applied to anRHCP feed of the downlink antenna. Each beam C comprises signal C in thefrequency band 18.3-18.8 GHz (500 MHz of spectrum for each such beam)applied to an LHCP feed of the downlink antenna, and each beam Dcomprises signal D in the frequency band 19.7-20.2 GHz (500 MHz ofspectrum for each such beam) applied to an LHCP feed of the downlinkantenna.

FIG. 1D illustrates a block diagram of a configuration for twotransmitters configured to transmit one set of the A, B, C, D (or 1, 2,3, 4) signals to the satellite downlink antenna beams of the four-colorreuse pattern of FIG. 1A. With reference to FIG. 1A, each of the beamsof the four-color reuse pattern corresponds to a respective one of theRF signals A, B, C, D (as transmitted by a respective transmitter ofFIG. 1D). Each of these four RF signals is transmitted by a feed on thedownlink satellite antenna to form Beams A, B, C, D. Each of thetransmitters comprises an amplifier 131, 151 (e.g., a traveling wavetube amplifier (TWTA)) and a filter 133, 153, and a circular polarizingfeed 135, 155. For example, the A+B RF signals (e.g., 1000 MHz) areamplified via the TWTA 131 and the C+D RF signals (e.g., 1000 MHz) areamplified by the TWTA 151. The amplified A+B and C+D signals are thenfed into the filters 133, 153, respectively, which separate the combinedA+B and C+D into separate A, B, C, D RF signals. Each filter output isconnected to a circular polarizing feed 135, 155, whereby the amplifiedA, B, C, D signals form two circularly polarized beams (e.g., of 500 MHzeach). For example, with reference to FIG. 1D, a right-hand polarizedBeam A (e.g., 500 MHz) and a right-hand polarized Beam B (e.g., 500 MHz)via the filter/polarizer 133/135, and a left-hand polarized Beam C(e.g., 500 MHz) and a left-hand polarized Beam D (e.g., 500 MHz) via thefilter/polarizer 153/155.

FIG. 1E illustrates example frequency band and polarization assignmentsfor the satellite downlink antenna beams of the three-beam reuse patternof FIG. 1B. Each Beam A comprises the RHCP signal for the frequency band18.2-19.2 GHz (1000 MHz of spectrum), each Beam B comprises the RHCPsignal for the frequency band 18.2-19.2 GHz (1000 MHz of spectrum), andeach Beam C comprises the LHCP and RHCP signals for the band 20.0-20.5GHz (500 MHz of spectrum at the each of the two polarizations RHCP andLHCP totaling 1000 MHz of spectrum). Note that, for this configuration,the ground terminals configured to receive the beam C would be requiredto have good cross-polarization discrimination.

FIG. 1F illustrates a block diagram of a configuration for twotransmitters configured to transmit one set of the A, B, C (or 1, 2, 3)signals to the satellite downlink antenna beams of the three-color reusepattern of FIG. 1B. With reference to FIG. 1B, each of the beams of thethree-color reuse pattern corresponds to a respective one of the RFsignals A, B, C (as transmitted by a respective transmitter of FIG. 1F).Each of these three RF signals is transmitted by a feed on the downlinksatellite antenna to form Beams A, B, C. Each of the transmitterscomprises an amplifier 171, 191 (e.g., a traveling wave tube amplifier(TWTA)), a filter 173, 193, and a circular polarizing feed 175, 195. Forexample, the Feed 1 RF signal (e.g., 1500 MHz) is amplified via the TWTA171 and the Feed 2 RF signal (e.g., 1500 MHz) is amplified by the TWTA191. The amplified signals are then each fed into the filters 173, 193,respectively, which separate the signals into the respective A, B, Cbeam RF signals. Each filter output is connected to a circularpolarizing feed 175, 195, whereby the amplified signals form therespective circularly polarized beams. For example, with reference toFIG. 1F, a right-hand polarized A beam (e.g., 1000 MHz) and a right-handpolarized partial C beam (e.g., 500 MHz) via the filter/polarizer173/175, and a left-hand polarized B beam (e.g., 1000 MHz) and aleft-hand polarized partial C beam (e.g., 500 MHz) via thefilter/polarizer 193/195. The spectrum of the two partial C beamscombine to provide a total C beam spectrum of 1000 MHz.

Satellite systems are generally designed to maximize capacity by usingall of the available spectrum. For example, if 1000 MHz of spectrum (inboth polarizations-right-hand polarization (RHCP) and left-handpolarization (LHCP)) is available for a particular system, the systemtheoretically has 2000 MHz of available spectrum for each beam group.With reference to the four-pattern reuse system of FIG. 1A, for example,each beam represented by the pattern 101 may comprise a RHCP of thefrequency band 18.3-18.8 GHz, each beam represented by the pattern 103may comprise a LHCP of the frequency band 18.3-18.8 GHz, each beamrepresented by the pattern 105 may comprise a RHCP of the frequency band19.7-20.2 GHz, and each beam represented by the pattern 107 may comprisea LHCP of the frequency band 19.7-20.2 GHz. Each beam would therebycomprise 500 MHz of spectrum or bandwidth, for a total availablecapacity of 2,000 MHz within each four-beam group. The reuse pattern canbe repeated as many times as desired, up to a maximum desired coverageregion, as limited by applicable physical constraints, such as totalpower and mass limits of the overall satellite payload. The total systembandwidth is then the sum of the individual bandwidths of all the beams.

The Ka frequency band downlink comprises 1500 MHz on each polarizationin the United States (U.S.) and as much as 2000 MHz in other regions. Inthe U.S., the Ka band is the band from 18.3-19.3 GHz and 19.7-20.2 GHz.In other regions, the Ka band may also include the band from 17.8-18.3GHz. In a satellite system that primarily serves the continental UnitedStates (CONUS), the band may be provided as a 3 color reuse plan byfrequency division. Specifically, each 1500 MHz may be divided into 6colors, amounting to 12 colors when factoring in both polarizations. The12 bands may then be grouped into three sets of four bands each, wherethe three sets are then routed through three distinct antennas on thesatellite. The three-color reuse may also be accomplished by providingall 3000 MHz via a single beam and time hopping the beam over 3 cells,so each cell receives 1000 MHz on average. This approach, however,suffers from the disadvantage of requiring that every feed on eachsatellite antenna be dual-pol (operate in both polarizations).

The size of a spot beam is determined primarily by the size of theantenna on the satellite—the larger the antenna, the smaller the spotbeam. Further, as would be recognized by one of ordinary skill in theart, in order to achieve reasonably acceptable RF performance, thenumber of beams and the reuse pattern employed will impose certainpayload design requirements, such as the number of antennae and the sizeof each antenna required to implement the desired beam pattern. To coverthe eastern half of the continental United States (CONUS), for example,one might design a satellite payload with 50 beams, each ofapproximately 0.5 degrees diameter, using a three-color reuse pattern.The antennas of such a payload might each be approximately 2.5 m indiameter and three or even four such antennae (e.g., 110 a, 110 b, 110c, 110 d) may be required to achieve desired RF performance. Each beammay be assigned 666 MHz, yielding a total of 33.3 GHz of bandwidth.Accordingly, the desired number of beams, reuse pattern and totalcapacity will contribute to payload size, weight and power requirements,which in turn will drive up the satellite manufacturing and launchcosts.

Moreover, in practice, the distribution of users and associated capacitydemand within the coverage area is non-uniform, which drives the goal ofa satellite system design to provide a corresponding non-uniformdistribution of capacity density to satisfy the respective demand.Accordingly, in recent times, some satellite system designs haveattempted to solve capacity density requirements by deploying suchsatellite technologies as steerable beams. FIG. 1G illustrates the fourpattern reuse plan of FIG. 1A, where the beams 1, 2, 3, 4 represent thepatterns 101, 103, 105, 107, respectively, and the beam pattern has beenoverlaid on a map of the Northeastern United States. As furtherillustrated in FIG. 1G, in order to provide higher capacity density tothe New York/Long Island, Southern Connecticut and Boston areas, certainof the beams have been steered to double the capacity over these regions(e.g., the 3 beam 121 has been moved to the cell 122, the 1 beam 123 hasbeen moved to the cell 124, the 3 beam 125 has been moved to the cell126, and the 2 beam 127 has been moved to the cell 128). Accordingly,the capacity density has been adjusted to double the spectrum/capacitydelivered to the cells 122, 124, 126, 128. This capacity densityadjustment, however, has been achieved at the expense of the capacitydelivered to the cells 121, 123, 125, 127—as spectrum cannot be providedto these cells without violating the adjacent cellpolarization/frequency requirements.

An alternative design may provide for a higher per-beam spectrumallocation. In view of such constraints as satellite size, weight andpower, however, such a design would limit the total number of beamsavailable at the higher spectrum allocation. Further, providing for suchhigh capacity beams also significantly increases satellite complexity.Accordingly, with this design, there may not be enough user beams tocover the contiguous United States, and thus the capacity would have tobe provided to the higher density population areas at the expense ofhaving no capacity provided to the lower density population areas (e.g.,providing user beams over only the Eastern and Western coasts of theUnited States. Accordingly, again, the desired capacity densityallocation is achieved at the expense of being unable to providecapacity to certain geographic regions.

What is needed, therefore, are approaches for flexible capacityallocation in satellite communications systems, without sacrificingcapacity in adjacent beams and without adverse impact with regard tosatellite size, weight, power and complexity constraints.

SOME EXAMPLE EMBODIMENTS

The present invention advantageously addresses the foregoingrequirements and needs, as well as others, by providing approaches fortime-based frequency reuse schemes in satellite communications systemsthat facilitate flexible capacity allocation, whereby capacity densityis dynamically adaptable in time across the different ground-based cellsof the system coverage area, without sacrificing capacity in adjacentbeams and without adverse impact with regard to satellite size, weight,power and complexity constraints. By way of example, such approachesavoid the partitioning of the frequencies of a particular polarization,thus eliminating filter requirements and reducing the satellite antennahardware complexity. By way of further example, dual polarization perantenna feed requirements are avoided in a frequency reuse scheme,whereby the total available frequency spectrum is provided to the cellsusing only a single filter per polarization, and time-based beams areapplied accordingly. For example, in a three-color reuse scheme, 3000MHz of spectrum is provided to the 3 cells using only a single 1500 MHzfilter per polarization, where each cell receives 1000 MHz on average.Alternatively, as a further example, this approach would also beapplicable to a case where 2000 MHz was available, or even a case wherethe same time-based beam crossed political boundaries such that 1500 MHzused part of the time and 2000 MHz was used at other times.

In accordance with example embodiments, a radio frequency (RF)communications transmitter system is provided. The RF communicationstransmitter system comprises at least one control processor, a switchand a plurality of feedhorns. The switch is configured to receive a feedsignal of a respective frequency bandwidth. The processor is configuredto control the switch to provide the feed signal received by the switchto each of at least two of the plurality of feedhorns for a respectivetime period. Each of the at least two of the plurality of feedhorns isconfigured to form and transmit a beam during the respective time periodthat the feed signal is provided to the feed horn, wherein the beam isformed based on the respective feed signal and is transmitted to cover arespective geographic area on and above the Earth. The formation andtransmission of the beams by the feedhorns is controlled by theprocessor to provide a time-based allocation of bandwidth amongst thebeams based on the respective time period that the feed signal isprovided to each of the at least two of the plurality of feedhorns and arespective frequency/polarization reuse scheme.

In accordance with further example embodiments, a radio frequency (RF)communications transmission method is provided. A switch of an RFcommunications transmitter system receives a feed signal of a respectivefrequency bandwidth. A processor controls the switch to provide the feedsignal received by the switch to each of at least two of a plurality offeedhorns of the RF communications transmitter system for a respectivetime period. Each of the at least two of the plurality of feedhornsforms and transmits a beam during the respective time period that thefeed signal is provided to the feedhorn, where the beam is formed basedon the respective feed signal and is transmitted to cover a respectivegeographic area on and above the Earth. The formation and transmissionof the beams by the feedhorns is controlled by the processor to providea time-based allocation of bandwidth amongst the beams based on therespective time period that the feed signal is provided to each of theat least two of the plurality of feedhorns and a respectivefrequency/polarization reuse scheme.

Still other aspects, features, and advantages of the present inventionare readily apparent from the following detailed description, simply byillustrating a number of particular embodiments and implementations,including the best mode contemplated for carrying out the presentinvention. The present invention is also capable of other and differentembodiments, and its several details can be modified in various obviousrespects, all without departing from the spirit and scope of the presentinvention. Accordingly, the drawing and description are to be regardedas illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention are illustrated by way ofexample, and not by way of limitation, in the figures of theaccompanying drawings, in which like reference numerals refer to similarelements, and in which:

FIG. 1A illustrates an example four-beam reuse pattern for a satellitecommunications system;

FIG. 1B illustrates an example three-beam reuse pattern for a satellitecommunications system;

FIG. 1C illustrates example frequency band and polarization assignmentsfor the beams of the four-beam reuse pattern of FIG. 1A;

FIG. 1D illustrates a block diagram of a configuration for twotransmitters configured to transmit one set of the A, B, C, D (or 1, 2,3, 4) signals to the satellite downlink antenna beams of the four-colorreuse pattern of FIG. 1A;

FIG. 1E illustrates example frequency band and polarization assignmentsfor the satellite downlink antenna beams of the three-beam reuse patternof FIG. 1B;

FIG. 1F illustrates a block diagram of a configuration for twotransmitters configured to transmit one set of the A, B, C (or 1, 2, 3)signals to the satellite downlink antenna beams of the three-color reusepattern of FIG. 1B;

FIG. 1G illustrates the four pattern reuse plan of FIG. 1A, where thebeam pattern has been overlaid on a map of the Northeastern UnitedStates;

FIG. 2 illustrates an example satellite communications system capable ofproviding approaches for a satellite communications system that employsspot beams of increased capacity density, in accordance with exampleembodiments of the present invention;

FIGS. 3A-3C illustrate a time-based three-color frequency reuse beampattern, where FIG. 3A depicts the pattern during a first Dwell Time(T1), FIG. 3B depicts the pattern during a second Dwell Time (T2) andFIG. 3C depicts the pattern during a third Dwell Time (T3), inaccordance with example embodiments of the present invention;

FIG. 3D illustrates time lines reflecting the three Dwell Times of thetime-based three-color frequency reuse beam pattern of FIGS. 3A-3C, inaccordance with example embodiments of the present invention;

FIG. 4A illustrates an example antenna transmitter implementation forthe time-based frequency reuse scheme of FIGS. 3A-3D, in accordance withexample embodiments of the present invention;

FIG. 4B illustrates an alternative example antenna transmitterimplementation for the time-based frequency reuse scheme of FIGS. 3A-3D,in accordance with example embodiments of the present invention;

FIG. 5 illustrates the beam/cell pattern of the time-based frequencyreuse scheme depicted in FIGS. 3A-3D overlaid on a map of theNortheastern United States, in accordance with example embodiments ofthe present invention;

FIG. 6 illustrates the cell structure of a satellite employing fourantennas, in accordance with example embodiments of the presentinvention;

FIG. 7A illustrates a three-color reuse pattern imposed on the fourantenna pattern of FIG. 5, in accordance with example embodiments of thepresent invention;

FIG. 7B illustrates an example amplifier assignment configuration forthe three-color reuse pattern of FIG. 7A, in accordance with exampleembodiments of the present invention;

FIG. 8 illustrates an example satellite transmitter implementation forthe three-color reuse scheme of FIG. 7B, in accordance with exampleembodiments of the present invention;

FIGS. 9A-9C illustrate diagrams depicting amplifier dwell timing for thethree-color reuse scheme of FIG. 7B, where FIG. 9A depicts the patternduring a first Dwell Time (T1), FIG. 9B depicts the pattern during asecond Dwell Time (T2) and FIG. 9C depicts the pattern during a thirdDwell Time (T3), in accordance with example embodiments of the presentinvention;

FIG. 9D illustrates time lines reflecting the three Dwell Times of thetime-based three-color frequency reuse beam pattern of FIGS. 9A-9C, inaccordance with example embodiments of the present invention; and

FIG. 10 illustrates an example processor control system for controllingthe operation and transmission of a time-based frequency reuse beamapproach, in accordance with example embodiments of the presentinvention.

DETAILED DESCRIPTION

Approaches for time-based frequency reuse schemes in satellitecommunications systems that facilitate flexible capacity allocation,whereby capacity density is dynamically adaptable in time across thedifferent ground-based cells of the system coverage area, withoutsacrificing capacity in adjacent beams and without adverse impact withregard to satellite size, weight, power and complexity constraints, areprovided. The present invention is not intended to be limited based onthe described embodiments, and various modifications will be readilyapparent. It will be apparent that the invention may be practicedwithout the specific details of the following description and/or withequivalent arrangements. Additionally, well-known structures and devicesmay be shown in block diagram form in order to avoid unnecessarilyobscuring the invention. Further, the specific applications discussedherein are provided only as representative examples, and the principlesdescribed herein may be applied to other embodiments and applicationswithout departing from the general scope of the present invention.

Further, as will be appreciated, a module or component (as referred toherein) may be composed of software component(s), which are stored in amemory or other computer-readable storage medium, and executed by one ormore processors or CPUs of the respective devices. As will also beappreciated, however, a module may alternatively be composed of hardwarecomponent(s) or firmware component(s), or a combination of hardware,firmware and/or software components. Further, with respect to thevarious example embodiments described herein, while certain of thefunctions are described as being performed by certain components ormodules (or combinations thereof), such descriptions are provided asexamples and are thus not intended to be limiting. Accordingly, any suchfunctions may be envisioned as being performed by other components ormodules (or combinations thereof), without departing from the spirit andgeneral scope of the present invention. Moreover, the methods, processesand approaches described herein may be processor-implemented usingprocessing circuitry that may comprise one or more microprocessors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), or other devices operable to be configured orprogrammed to implement the systems and/or methods described herein. Forimplementation on such devices that are operable to execute softwareinstructions, the flow diagrams and methods described herein may beimplemented in processor instructions stored in a computer-readablemedium, such as executable software stored in a computer memory store.

Further, terminology referring to computer-readable media or computermedia or the like as used herein refers to any medium that participatesin providing instructions to the processor of a computer or processormodule or component for execution. Such a medium may take many forms,including but not limited to non-transitory non-volatile media andvolatile media. Non-volatile media include, for example, optical storagemedia, magnetic storage media or electrical storage media (e.g., solidstate storage media). Volatile media include dynamic memory, such randomaccess memory or RAM, and non-volatile memory include memory such asprogrammable read only memory (PROM), erasable PROM, flash EPROM, anyother memory chip or cartridge, or any other such medium from which aprocessor can read data.

Further, while the following example embodiments comprise application ofthe concepts of the present invention to a satellite transmissionsystem, the invention is not limited to only satellite applications.Instead, the concepts of the present invention are applicable to anywireless radio frequency (RF) communications platform that provides datacommunications services via one or more discrete radio frequencycommunications beams. By way of example, the concepts of the inventionare applicable to high altitude platforms (HAPs) for wirelesstelecommunications. A HAP generally operates in a quasi-stationaryposition at altitudes of upwards of 22 kilometers (typically 17-22 km).Such a HAP will carry a communications payload somewhat akin to asatellite payload. HAPS, however, operate at much lower altitudes thansatellites, making it possible to cover smaller regions moreeffectively, for example, via radio frequency communications beams. AHAP may also relay data communications via a satellite (e.g., ageostationary orbit satellite or a low earth orbit satellite).

FIG. 2 illustrates an example satellite communications system capable ofproviding approaches for a satellite communications system that employsspot beams of increased capacity density, in accordance with exampleembodiments of the present invention.

The satellite communications system includes one or more satellites (ofwhich two are shown in the Figure—satellites 232 a and 232 b) thatsupport communications among multiple satellite terminals (STs) 234a-234 n, a number of gateways (GWs) 238 a-238 n, and a networkoperations center (NOC) 242. The STs, GWs and NOC transmit and receivesignals via the antennas 236 a-236 n, 246 a-246 n, and 256,respectively. According to different embodiments, the NOC 242 may resideat a separate site reachable via a separate satellite channel or mayreside within a GW site. The NOC 242 performs the management planefunctions of the system 230, while the GWs 238 a-238 n perform the dataplane functions of the system 230. For example, the NOC 242 performssuch functions as network management and configuration, softwaredownloads (e.g., to the STs 234 a-234 n), status monitoring, statisticsfunctions (e.g., collection, aggregation and reporting), securityfunctions (e.g., key generation, management and distribution), STregistration and authentication, and GW diversity management. The NOC242 communicates with each GW via the satellite 232, or via a secureprivate communications network 252 (e.g., an IPsec tunnel over adedicated link or a virtual private network (VPN) or IPsec tunnelthrough a public network, such as the Internet). It should be notedthat, according to one example embodiment, the traffic classificationapproaches of embodiments of the present invention addressclassification of data traffic flowing through an aggregation point ornode. Additionally, each GW and the NOC have connectivity to one or morepublic communications networks, such as the Internet or a PSTN.

According to a further example embodiment, each of the GWs 238 a-238 ninclude one or more IP gateways (IPGWs)—whereby the data plane functionsare divided between a GW and its respective IPGWs. For example, GW 238 aincludes IPGWs 248 a(1)-248 a(n) and GW 238 n includes IPGWs 248n(1)-248 n(n). A GW may perform such functions as link layer andphysical layer outroute coding and modulation (e.g., DVB-S2 adaptivecoding and modulation), link layer and physical layer inroute handling(e.g., IPOS), inroute bandwidth allocation and load balancing, outrouteprioritization, web acceleration and HTTP compression, flow control,encryption, redundancy switchovers, and traffic restriction policyenforcement. Accordingly, an inroute manager or inroute group manager(IGM) (not shown) may be located at each of the gateways. The IGM may beconfigured to control the bandwidth allocations to the remote terminals(e.g., on an inroute or inroute group basis), and to correspondinglycontrol and administer the bandwidth allocation approaches provided inaccordance with the example embodiments of the present invention.Further, as would be appreciated, in certain embodiments, the IGM may bedeployed in a distributed manner, with a main controller at the NOC 242,whereby the NOC may be configured to administer system-wide controls forsuch bandwidth allocation approaches, whereas the inroute-based controlswould be administered for specific inroutes/inroute groups by the IGM atthe respective gateway that controls such inroutes/inroute groups.Various other architectures may also be provided to meet respectivedifferent system design goals and requirements.

The IPGW may perform such functions as data compression, TCP performanceenhancements (e.g., TCP performance enhancing proxies, such as TCPspoofing), quality of service functions (e.g., classification,prioritization, differentiation, random early detection (RED), TCP/UDPflow control), bandwidth usage policing, dynamic load balancing, androuting. Further, a GW and respective IPGW may be collocated with theNOC 242. The STs 234 a-234 n provide connectivity to one or more hosts244 a-244 n and/or routers 254 a-254 n, respectively. The Satellitecommunications system may operate as a bent-pipe system, where thesatellite essentially operates as a repeater or bent pipe.Alternatively, the system may employ a switching or processing satellitesupporting mesh communications (point-to-point communications directlybetween, for example, the two STs 234 a and 234 n).

In a bent-pipe system of an example embodiment, the satellite 232operates as a repeater or bent pipe, and communications to and from theSTs 234 a-234 n are transmitted over the satellite 232 to and fromrespective IPGWs associated with particular STs. Further, in a spot beamsystem, any one spot beam operates as a bent-pipe to geographic regioncovered by the beam. For example, each spot beam operates as a bent pipecommunications channel to and from the STs and/or IPGW(s) within thegeographic region covered by the beam. Accordingly, signal transmissionsto the satellite are either from an ST and destined for an associatedgateway, or from a gateway and destined for an associated ST. Accordingto one embodiment, several GWs/IPGWs are distributed across thegeographic region covered by all spot beams of the satellite 232, where,in a beam in which a GW (and respective IPGWs) are located, only the oneGW (and no STs) occupies that beam. Further, each IPGW may serve as anaggregation node for a multitude of remote nodes or STs. The totalnumber of GWs/IPGWs, and the geographic distribution of the GWs/IPGWs,depends on a number of factors, such as the total capacity of thesatellite dedicated to data traffic, geographic traffic loading of thesystem (e.g., based on population densities and the geographicdistribution of the STs), locations of available terrestrial datacenters (e.g., terrestrial data trunks for access to public and privatededicated networks). More specifically, for a data communication from ST234 a to a public communications network 258 (e.g., the Internet), theST 234 a is associated with an IPGW (e.g., IPGW 248 a(1)—selected from apool of IPGWs available to the ST 234 a, such as IPGWs 248 a(1)-248a(7)—where the pool of IPGWs is a suitable subset of the IPGWs 248a(1)-248 a(n) located at the GW 238 a). The data is first transmitted,via the satellite 232, from the ST 234 a to associated IPGW 248 a(1).The IPGW 248 a(1) determines the destination as being the Internet 258.The IPGW then repackages the data (e.g., as a TCP/IP communication), androutes the data communication, via the terrestrial link 264, to theInternet 258.

FIGS. 3A-3C illustrate a time-based three-color frequency reuse beampattern, where FIG. 3A depicts the pattern during a first Dwell Time(T1), FIG. 3B depicts the pattern during a second Dwell Time (T2) andFIG. 3C depicts the pattern during a third Dwell Time (T3), inaccordance with example embodiments of the present invention. Eachhexagon represents a cell/beam in a frequency reuse system. Cells of thesame shade/color (where each of the different colors is represented inthe Figures as a respective shade of gray and/or patterning) representgeographic areas (on the ground) in which service is provided to userterminals using the same satellite frequency and polarization at thesame time. For example, (i) the lighter shaded cells 311 (e.g.,corresponding to Color-1) reflect beams of a frequency band at a firstpolarization (e.g., RHCP, as depicted) illuminating the respective cellsduring the dwell times T1 and T2, (ii) the darker shaded cells 313(e.g., corresponding to Color-2) reflect beams of the frequency band ata second polarization (e.g., LHCP, as depicted) illuminating therespective cells during the dwell times T1 and T3, (iii) the darkershaded cross-hatched cells 315 (e.g., corresponding to Color-3A) reflectbeams of the frequency band at the first polarization (e.g., RHCP, asdepicted) illuminating the respective cells during only the dwell timeT2, and (iv) the lighter shaded cross-hatched cells (e.g., correspondingto Color-3B) reflect beams of the frequency band at the secondpolarization (e.g., LHCP, as depicted) illuminating the respective cellsduring only the dwell time T3. The Color-3A and Color-3B together areconsidered as one color of the three-color reuse scheme FIG. 3Dillustrates time lines reflecting the three Dwell Times of thetime-based three-color frequency reuse beam pattern of FIGS. 3A-3C, inaccordance with example embodiments of the present invention.

According to one example embodiment, the version of the time-based reusesystem shown in FIGS. 3A-3D may be provided from three antennas. By wayof example, there would be a 1:1 correspondence between the antenna andthe color, where the Color-1 cells 311 are served from a first antenna(A1), the Color-2 cells are served from a second antenna (A2) and theColor-3 cells are served from a third antenna (A3). By way of furtherexample, the Antenna A1 exclusively uses the right hand circularpolarization (RHCP) and the Antenna A2 exclusively uses the left handcircular polarization (LHCP). The Antenna A3 uses both RHCP and LHCP,but not at the same time in the same cell. Whenever a cell is active, itreceives the full frequency spectrum on whichever polarization is inuse—in this example, each Antenna A1 beam provides the full spectrumwith RHCP, each Antenna A2 beam provides the full spectrum with LHCP,and each Antenna A3 beam provides the full spectrum with RHCP duringcertain dwell times and with LHCP during certain other dwell times.Accordingly, on the ground, each terminal need only receive/transmit atone polarization depending on the uplink/downlink beams to which theterminal is assigned.

Further, assuming that the frequency band provides 1500 MHz of spectrum,the cells 311 and 313 receive 1500 MHz two-thirds of the time (the cells311 at RHCP, and the cells 313 at LHCP), and the cells 315/317 alsoreceive 1500 MHz two-thirds of the time (one-third at RHCP and one-thirdat LHCP). With reference to FIG. 3A, during dwell time T1 (one-third ofthe time), the Antenna A1 transmits 1500 MHz (at RHCP) into the Color-1beams 311 and the Antenna A2 transmits 1500 MHz (at LHCP) into theColor-2 beams 313. The Antenna A3 is not transmitting during dwell timeT1. With reference to FIG. 3B, during dwell time T2 (one-third of thetime), the Antenna A1 transmits 1500 MHz (at RHCP) into the Color-1beams 311 and the Antenna A3 transmits 1500 MHz (at LHCP) into theColor-3A beams 315. The Antenna A2 is not transmitting during dwell timeT2. With reference to FIG. 3C, during dwell time T3 (one-third of thetime), the Antenna A2 transmits 1500 MHz (at LHCP) into the Color-2beams 313 and the Antenna A3 transmits 1500 MHz (at RHCP) into theColor-3B beams 317. The Antenna A1 is not transmitting during dwell timeT3. Accordingly, during each dwell time, only two of the three antennaeare transmitting and each is transmitting at a different polarizationfrom the other. Over the three dwell times, the Color-1 cells receive1500 MHz for 2 of the 3 dwell times (nominally 1000 MHz on average), theColor-2 cells receive 1500 MHz for 2 of the 3 dwell times (nominally1000 MHz on average), and the Color-3 cells receive 1500 MHz for 2 ofthe 3 dwell times (nominally 1000 MHz on average). Accordingly, thisapproach of this example reflects a uniform three-color reuse scheme.

FIG. 4A illustrates an example antenna transmitter implementation forthe time-based frequency reuse scheme of FIGS. 3A-3D, in accordance withexample embodiments of the present invention. With reference to FIG. 4A,for example, a forward or outroute direction (a gateway uplink to thesatellite, which is split into multiple downlink beams for transmissionto the user terminals located amongst the multiple beams). Each feedsignal, which illuminates a single beam (a single feed per beamapproach) connects to a TWTA and then to a switch. While the specificimplementation of the waveguide connections of the feed to the TWTA andto the switch are not shown by the Figure in detail, different potentialimplementations would be appreciated and achievable (based on antennadesign considerations) by one of skill in the art. The switch routes thefull spectrum (e.g., 1500 MHz) of the feed signal to the respectivepolarizing feed for each individual downlink beam of the respectivecolor for a respective dwell time. With regard to the Color-3 beams, theswitch has two outputs for each beam (one output for each of the twopolarizations), where each beam is being transmitted at only one of thepolarizations during a respective dwell time. By way of example, thehorns for each beam of the Antenna A1 and of the Antenna A2 may besingle-pole horns, whereas the horns for each beam of the Antenna A3 maybe dual-pole horns.

FIG. 4B illustrates an alternative example antenna transmitterimplementation for the time-based frequency reuse scheme of FIGS. 3A-3D,in accordance with example embodiments of the present invention. Withreference to FIG. 4B, the antenna implementation for this reuse schemedoes not require TWTA amplifiers. Instead, it can be implemented withSSPA or other devices. The main difference is that the switch would belocated before the SSPA rather than after the TWTA (as illustrated inthe Figure). In FIG. 4B, the depiction of the Beams 2 thru N for theColor-1 beams and for the Color-2 beams are each shown as a single 1500MHz SSPA feed for simplicity and to fit them in the figure—however, aswould be appreciated (in practice) each individual Color-1 and Color-2beam would be implemented as a separate SSPA per-feed (as shown for theColor-3 beams of FIG. 4B).

Further, in accordance with the time-based three-color reuse exampledescribed above with reference to FIGS. 3A-3D, the various dwell timesof the respective beams may be configured in any manner to adjust thecapacity distribution amongst the beams. For example, the Antenna A1Beam 1 may be active two-thirds of the time (e.g., illuminating the celllabeled 311)—this leaves the A1_Feed-1 signal spectrum free forone-third of the time to serve other beams illuminated from the AntennaA1 (depicted as the Antenna A1 (Color-1) Beams 2 thru N in FIGS. 4A and4B), which may share the remaining one-third time in any desired mannersubject to the distance/interference constraints of such a three-colorreuse scheme. Similarly, the Antenna A2 Beam 1 may be active two-thirdsof the time (e.g., illuminating the cell labeled 313)—this leaves theA2_Feed-1 signal spectrum free for one-third of the time to serve otherbeams illuminated from the Antenna A2 (depicted as the Antenna A2(Color-2) Beams 2 thru N in FIGS. 4A and 4B), which also may share theremaining one-third time in any desired manner subject to thedistance/interference constraints of such a three-color reuse scheme.The Antenna A3 Beam 1 may be active one-third of the time fortransmission at a first polarization (e.g., the Color-3B RHCP beamilluminating the cell labeled 317) and one-third of the time fortransmission at a second polarization (e.g., the Color-3A LHCP beamilluminating the cell labeled 315)—this leaves the A3_Feed-1 signal TWTAfree for one-third of the time to serve other beams illuminated from theAntenna A3 (depicted as the Antenna A3 Beams 2 thru N in FIGS. 4A, 4B),which may share the remaining one-third time in any desired mannersubject to the distance/interference constraints of such a three-colorreuse scheme. Further, as would be recognized, the various dwell timesor percentages shown in FIG. 4A may be altered in any manner to changethe capacity distribution amongst the beams.

FIG. 5 illustrates the beam/cell pattern of the time-based frequencyreuse scheme depicted in FIGS. 3A-3D overlaid on a map of theNortheastern United States, in accordance with example embodiments ofthe present invention. By way of example, the Antenna A1 Beam 1 may bedirected at the cell 501 covering northern New Jersey, New York City andeastern Long Island (e.g., Brooklyn), the Antenna A2 Beam 1 may bedirected at the cell 503 covering eastern Long Island, Connecticut andwestern Rhode Island, and the Antenna A3 Beam 1 may be directed at thecell 505 covering eastern Massachusetts (including Boston and the Cape).With this configuration (as shown in FIGS. 3A-3D and 4A-4B, and theexample of 1500 MHz per beam), the major metropolitan areas of highpopulation density (e.g., northern Jersey, New York City, western LongIsland, Boston, etc.) within the cells 501, 503, 505 would be covered bythe full 1500 MHz of spectrum of the feed signals A1_Feed-1, A2_Feed-1and A3_Feed-1, respectively, for a total dwell time for each cell oftwo-thirds of the time that the respective antenna is transmitting(e.g., effectively ⅔×1500=1000 MHz). Additionally, the 1500 MHz of eachof the three feed signals A1_Feed-1, A2_Feed-1 and A3_Feed-1 for theremaining one-third of dwell time can be respectively shared by a numberof additional beams, provided that the transmit feed for each such beamis connected to the same switch as the respective feed, and thatapplicable frequency reuse constraints are not violated. For example,the Antenna A1 Beams 2 and 3 may be directed at the cells 507 and 509,respectively, each for a dwell time of one-sixth of the time that theAntenna A1 is transmitting (e.g., effectively ⅙×1500=250 MHz to eachcell). Similarly, the Antenna A2 Beams 2 and 3 may be directed at thecells 511 and 513, respectively, each for a dwell time of one-sixth ofthe time that the Antenna A2 is transmitting (e.g., effectively⅙×1500=250 MHz to each cell). Also, the Antenna A3 Beams 2 and 3 may bedirected at the cells 515 and 517, respectively, each for a dwell timeof one-sixth of the time that the Antenna A3 is transmitting (e.g.,effectively ⅙×1500=250 MHz to each cell). Alternatively, the Antenna A3Beams 2 and 3 may be directed at the cells 515, 517, 519, 521,respectively, each for a dwell time of one-twelfth of the time that theAntenna A3 is transmitting (e.g., effectively 1/12×1500=125 MHz to eachcell). By way of example, the diameter of a cell/beam may be on theorder of 110-200 km.

In accordance with such example embodiments, the capacity can thus beflexibly allocated across the cell pattern of the satellite antennae.Further, the allocation may be preprogrammed via a dwell time plan foreach feed of each antenna. Additionally, the capacity allocations can bedynamically updated to address various circumstances, such as weatherchanges that may trigger a need to adjust capacity allocations ofaffected cells, changes in system loading over time (e.g., based onchanges in subscriber numbers and associated user population densitiesacross the geographical area of the subscriber base, antenna elementfailures, etc. Also, traffic demand may also change due to mobility(e.g., traffic for aircraft or other mobile internet services).Accordingly, such time-based frequency reuse and capacity allocationpermits the varying of the capacity allocations continually while thesatellite is in operation (on orbit)—the time-based capacity plan can bedynamically programmed and modified over time. Further, the flexibilityfacilitated by embodiments of the present invention is achieved in asimple manner, for example, by employing analog switches to switch thefeed amongst the different beam outputs based on a beam allocation timeplan.

By contrast, with a traditional filter architecture, dynamic adaptationof capacity allocation in such a manner would require dynamic adaptationof the bandwidth passed through a filter for a particular beam. Suchfilter adaptation is impossible with individual fixed analog filteringcircuits, and would thus require multiple filter circuits of differentbandwidths and a switching component to switch between the filtersdepending on the desired bandwidth for a beam. Such an approach wouldsignificantly increase the complexity and hardware requirements of thecircuitry for each beam—and multiplied by, for example, 100 beams wouldsignificantly increase the complexity, cost, size and weight of thesatellite payload (likely beyond reasonable or even absolute limits). Analternative approach would be to employ digital signal processing forthe filtering of the feed for each beam, which would similarly imposesignificant adverse impacts on the complexity, cost, etc. of theantenna. Programmable digital filters are consistent with state of theart, however their mass and power requirement far exceed that of thesimple switches proposed herein.

In further accordance with such example embodiments, as would berecognized, while the embodiments of the Figures show antennaconfigurations with one uplink feed and switch per antenna, in practice,each antenna would support a number of uplink or input feeds and anumber of switches, with each switch feeding a respective number ofdownlink beams. Further, the number of input feeds of a given antenna,for example, in the case of the forward link, may depend on the numberof gateway locations or feederlink beams that the antenna is required toservice. Similarly, the number of downlink feeds of a given antenna, forexample, again in the case of the forward link, may depend on therequired coverage area of the antenna, the bandwidth of each beam feedand the number of downlink cells desired to cover the area. As would befurther appreciated, the number of input and output feeds of each switchmay depend on such factors as the switch technology, the ultimate layoutof the downlink beams of the respective antenna and the frequency reuseconfiguration of the beams, and the resulting geometry and layout of theantenna components (e.g., required waveguides for the switch connectionsmay be restricted by antenna space constraints). Further, the systemthereby provides for virtually unlimited flexibility, limited only bydesign constraints arising from the implementation of the satellite andantenna—e.g., size, weight and power constraints of the overallsatellite implementation, and physical constraints arising from theantenna technology (e.g., the switch technology, the waveguidetechnology and the overall layout of the antenna). The input feed,switch and output beam configurations (e.g., the number of input feedsand output beams of a switch) can be laid out to facilitate a tremendousamount of flexibility in the allocation of capacity amongst a widedispersal of the beams. Further, the limit on the flexibility is basedon the specific feeds attached to each switch. Within that group, thedownlink time and data rate for each beam is flexible but cannot exceedthe total spectrum. So, the fixed assignment of a set of beams to aswitch is a limitation. By way of further example, however, anadditional layer of switching could add further flexibility—in otherwords switches could be interconnected.

As would be further understood, the number of desired beams, the widthof the beams, and the desired beam pattern (e.g., covering thecontinental United States) would be limited in part by the antenna size(the feed horn cluster size and the related reflector size). With regardto the three antennae time-based three-color reuse example (describedabove), for example, each antenna may illuminate its respective patternof one-third of the cells of an overall cell pattern covering the UnitedStates (based on the cells that each antenna illuminates). Consideringthe focal point of each feed and the principles of geometrical optics,the location of a particular beam on the Earth's surface, from arespective feed horn, depends on the location of the horn within thefeed cluster of the antenna—the physical position of the feed relativeto the antenna reflector determines the location of the resulting beamon the surface of the Earth. Accordingly, the beam spacing on thesurface of the Earth depends on the spacing of the horns in the feedcluster, where the spacing will generally be constrained by certainfactors, including the size of the feed horn, the available space of thefeed cluster, the number of desired beams and the pattern of the overallcoverage area. Also, the larger the antenna (reflector), the smaller thebeam. A larger feed horn, on the other hand, illuminates a smaller partof the antenna than a small feed would. So the antenna “looks smaller”and produces a larger beam. In other words, larger feed, larger beam.Conversely, making a feed really small will illuminate “more” than theentire antenna (reflector) resulting in “spillover” or“over-illumination.” Basically, a lot of the energy from the feed goes“past” the antenna and doesn't radiate towards Earth. Moreover, theantenna design must also factor in the polarizer and waveguide inputs atthe back of the feed horns, which also consume real estate in thephysical antenna implementation. Therefore, the number of beam and thebeam size, and the desired pattern (e.g., three-color reuse) and overallcoverage area on the surface of the Earth, will drive the antenna sizefor each antenna, and thus will also be constrained by physical limitson the antenna size. Further, the beam design requirements will thusalso determine/drive the number of antennae of the satellite design(more antennae can be used to achieve an increased number of narrowerbeams)—and will similarly be limited by the satellite size, weight andpower constraints.

Accordingly, example embodiments of the present invention facilitateflexible capacity allocation, whereby capacity density is dynamicallyadaptable in time across the different ground-based cells of the systemcoverage area, without sacrificing capacity in adjacent beams andwithout adverse impact with regard to satellite size, weight, power andcomplexity constraints. For example, such approaches avoid thepartitioning of the frequencies of a particular polarization, thuseliminating filter requirements and reducing the satellite antennahardware complexity. With a typical single feed per beam satelliteantenna architecture. In order to divide the spectrum of a feed andallocate portions of the spectrum across different beams (especially inthe case where the partitioning is not evenly allocated across thebeams), complex filtering is required.

FIG. 6 illustrates the cell structure of a satellite employing fourantennas, in accordance with example embodiments of the presentinvention. The Figure shows an example cell structure achieved usingfour antennas, where each pattern illustrated in FIG. 6 represents thecells served by a respective one of the four antennae. The horizontaldash pattern 611 represents the cells served by the first antenna, thevertical dash pattern 613 represents the cells served by the secondantenna, the vertical line pattern 615 represents the cells served bythe third antenna, and the horizontal line pattern 617 represents thecells served by the fourth antenna.

FIG. 7A illustrates a three-color reuse pattern imposed on the fourantenna pattern of FIG. 5, in accordance with example embodiments of thepresent invention. The three colors are represented by the light grayshade (Color-1) 711, the dark gray shade (Color-2) 713 and no gray shade(Color-3) 715, and the four antennae are again represented by the fourdifferent line patterns, respectively. Note that each color appears oneach antenna.

FIG. 7B illustrates an example amplifier assignment configuration forthe three-color reuse pattern of FIG. 7A, in accordance with exampleembodiments of the present invention. By way of example, the darkershaded cell with the vertical stripes (cell 721) may use amplifier 1 toprovide the Color-2 frequency/polarization during two-thirds of thetime. The lighter shaded cell with the vertical stripes (cell 723) mayuse amplifier 2 to provide the Color-1 frequency/polarization duringtwo-thirds of the time. This does not cause interference because theyare using opposite polarizations. During the remaining one-third of thetime, the cell 725 may use a combination of amplifiers 1 and 2 toprovide the Color-3 frequency/polarization. By way of further example,the cell 725 may be generated by a dual pole feed adjacent to bothamplifiers 1 and 2, which minimizes the waveguide run lengths and doesnot require additional switches (since it is a dual pole feed). Theremaining cells of FIG. 7B may be generated in similar manners with theillustrated amplifier assignments.

FIG. 8 illustrates an example satellite transmitter implementation forthe three-color reuse scheme of FIG. 7B, in accordance with exampleembodiments of the present invention. With this approach, for example,the amplifier TWTA 1 may service the Color-1/Beam-A two-thirds of thetime, the amplifier TWTA 2 may service the Color-2/Beam-B two-thirds ofthe time, and the dual feed of the TWTA 1 and TWTA 2 may togetherservice the Color-3/Beam-C one-third of the time (where the TWTA 1services the beam via RHCP and the TWTA 2 services the beam via LHCP).

FIGS. 9A-9C illustrate diagrams depicting amplifier dwell timing for thethree-color reuse scheme of FIG. 7B, where FIG. 9A depicts the patternduring a first Dwell Time (T1), FIG. 9B depicts the pattern during asecond Dwell Time (T2) and FIG. 9C depicts the pattern during a thirdDwell Time (T3), in accordance with example embodiments of the presentinvention. The illustrated amplifier timing reflects the operation ofjust one antenna. The other three antennas operate in the same manner,but offset in space. Each figure shows how amplifiers “A” and amplifiers“B” are switched from one dwell time to the next for the three dwelltimes.

FIG. 9D illustrates time lines reflecting the three Dwell Times of thetime-based three-color frequency reuse beam pattern of FIGS. 9A-9C, inaccordance with example embodiments of the present invention. As withthe example embodiment of FIGS. 3A-3D, the A and B cells each receivethe full spectrum (e.g., 1500 MHz) two-thirds of the time, and the A/Bhorizontal-lined cells A/B also receive the full spectrum (e.g., 1500MHz) two-thirds of the time.

The four antenna time-based three-color reuse approach of FIGS. 6-9thereby achieves even further enhanced flexibility in the capacityallocation amongst the beams. This enhanced flexibility arise from theability to switch a particular TWTA from a one of the three color beams(at the respective frequency/polarization pair) to a different one ofthe three color beams (at the different respectivefrequency/polarization pair) transmitted from the same antenna (from thesame feed array). Whereas, with the three antenna approach (describedabove with reference to FIGS. 3-5), because each of the three antennaeserviced only one color of the three-color reuse scheme, switching agiven TWTA from a beam of one color to a beam of a different color wouldrequire switching the TWTA from one antenna (servicing the beams of thefirst color) to a different antenna (servicing the beams of the othercolor). Switching a given TWTA between different antennae—however, basedon antenna/satellite design constraints, would be extremely difficultand inefficient (if not impossible) to facilitate. A beam of a desiredEquivalent Isotropic Radiated Power (EIRP) requires a respective TWTAamplification level (which depends in part on the power loss due to thewaveguide run between the TWTA and the beam horn), and thus thewaveguide run from the TWTA to the horn should be minimized in order tominimize power loss. Accordingly, for a given antenna, the TWTAs areideally located in positions to minimize the waveguide runs to therespective switches serving the beams of that antenna that the TWTAswill drive, and providing for the ability to switch a particular TWTA toa horn of a different antenna would require too long of a waveguide runto effectively preserve enough power to transmit the respective beam atthe desired EIRP (also, such waveguide runs would likely also add toomuch complexity, size, space and weight to the overall antennaeimplementations).

Moreover, an additional benefit of transmitting 1500 MHz at all times tothe active beam is to overcome interference occurring in a shared band.For example, the 17.8-18.3 GHz band is shared between terrestrialmicrowave and the satellite downlink. If a particular satellite receiverexperiences significant interference from a nearby microwave tower, thatreceive can use a carrier in a different portion of the downlink band.Similarly, if the Ka-band downlink frequency allocation differs betweencountries, the satellite transmitter can enable or disable a portion ofthe band accordingly without violating any reuse constraints.

Further, the time-based approach does not necessarily imply that thespectrum being transmitted from a single amplifier remain constant. Forexample, a TWTA may serve some beams that can use 2000 MHz and otherbeams that can use 1500 MHz. This change would be accomplished byturning carriers on and off at the terrestrial transmitter withoutneeding to make any changes on the satellite.

This technique could also be used in a hybrid configuration in whichsome beams were time-based and some beams were fixed. The fixed reusepattern would have less than 1500 MHz per beam but on all the time. Thiswould create frequency reuse conflicts that need to be resolved in somefashion. One technique would be to change the bandwidth used during timeperiods for beams in the transition region between fixed and time-basedreuse.

FIG. 10 illustrates an example processor control system 1000 forcontrolling the operation and transmission of a time-based frequencyreuse beam approach, in accordance with example embodiments of thepresent invention. The processor control system includes, for instance,a processor 1003 and memory 1005 incorporated in one or more physicaldevices. By way of example, as specified above, suchprocessor-implemented control circuitry may comprise one or moremicroprocessors, application specific integrated circuits (ASICs), fieldprogrammable gate arrays (FPGAs), or other devices operable to beconfigured or programmed to implement the systems and/or methodsdescribed herein. For implementation on such devices that are operableto execute software instructions, the flow diagrams and methodsdescribed herein may be implemented in processor instructions stored ina computer-readable medium, such as executable software stored in acomputer memory store. By way of further example, the memory maycomprise any medium that participates in providing instructions to theprocessor which may take many forms, including but not limited tonon-transitory non-volatile media and volatile media. Non-volatile mediainclude, for example, optical storage media, magnetic storage media orelectrical storage media (e.g., solid state storage media). Volatilemedia include dynamic memory, such random access memory or RAM, andnon-volatile memory include memory such as programmable read only memory(PROM), erasable PROM, flash EPROM, any other memory chip or cartridge,or any other such medium from which a processor can read data.

According to example embodiments, the memory may store programinstructions and operational and control data for controlling thesatellite transmitters to process the feed signals and transmit thebeams of a time-based frequency reuse approach of such exampleembodiments. In that regard, the processor may execute control programsand provide resulting control signaling to the satellite transmittersfor controlling the transmitters to process the feed signals andtransmit the beams of a particular time-based frequency reuse approach.Further, the processor may further be controlled from a ground-based NOC(e.g., the NOC 242 of FIG. 2). In that regard, the NOC may providecommand signaling for initial configuration and programming ofparticular time-based frequency reuse approaches to be implemented bythe satellite payload. Further, the NOC may also provide commandsignaling for dynamic control and reconfiguration of the particulartime-based frequency reuse approaches to be implemented by the satellitepayload.

While example embodiments of the present invention may provide forvarious implementations (e.g., including hardware, firmware and/orsoftware components), and, unless stated otherwise, all functions areperformed by a CPU or a processor executing computer executable programcode stored in a non-transitory memory or computer-readable storagemedium, the various components can be implemented in differentconfigurations of hardware, firmware, software, and/or a combinationthereof. Except as otherwise disclosed herein, the various componentsshown in outline or in block form in the figures are individually wellknown and their internal construction and operation are not criticaleither to the making or using of this invention or to a description ofthe best mode thereof.

In the preceding specification, various embodiments have been describedwith reference to the accompanying drawings. It will, however, beevident that various modifications may be made thereto, and additionalembodiments may be implemented, without departing from the broader scopeof the invention as set forth in the claims that follow. Thespecification and drawings are accordingly to be regarded in anillustrative rather than restrictive sense.

What is claimed is:
 1. A radio frequency (RF) communications transmittersystem comprising: at least one control processor; a switch; and aplurality of feedhorns; and wherein the switch is configured to receivea feed signal of a respective frequency bandwidth; wherein the processoris configured to control the switch to provide the feed signal receivedby the switch to each of at least two of the plurality of feedhorns fora respective time period; wherein each of the at least two of theplurality of feedhorns is configured to form and transmit a beam duringthe respective time period that the feed signal is provided to thefeedhorn, wherein the beam is formed based on the respective feed signaland is transmitted to cover a respective geographic area on and abovethe Earth; and wherein the formation and transmission of the beams bythe feedhorns is controlled by the processor to provide a time-basedallocation of bandwidth amongst the beams based on the respective timeperiod that the feed signal is provided to each of the at least two ofthe plurality of feedhorns and a respective frequency/polarization reusescheme.